1. Field of the Invention
This invention relates to squaring tools used by carpenters and particularly to speed squares used to determine and mark the correct base cut angle for rafters and the like.
2. Description of the Prior Art
Base Cut Marks
Numerous roofing speed squares and templates have been devised over the years to enable the roofing carpenter to mark and cut the base cut of a rafter. The rafter base cut is a horizontal cut at the bottom extreme of the rafter. The angle between the base cut and the longitudinal axis of the rafter is a function of the slope of the roof.
The speed square currently enjoying the greatest usage by roofing carpenters in this country is Swanson's Marking Tool with Wear Rims (U.S. Pat. No. 4,742,619). Swanson's Marking Tool features a scale parallel to the tool hypotenuse which incorporates roof unit rise values typically ranging from 1 inch roof rise per foot roof run to 30 inches roof rise per foot roof run. This scale is used to mark the base cut angle of a rafter.
Swanson's Marking Tool is a bit cumbersome to use, in that 2 and more frequently 3 distinct steps are required to yield the straight line mark defining the rafter base cut location. This multiplicity of steps creates a number of problems: Time is wasted, any error in measurement is doubled or more often tripled (due to the 2 or 3 separate steps involved) which in the worst case may result in the scrapping of the board, etc.
Common Cut Marks
Roofing carpenters are frequently required to make rafter common cut marks while perched atop the roof under construction.
Two problem exists related to the use of currently available speed squares to make rafter common cut marks by roofing carpenters located atop a roof: firstly the pertinent scale on the speed square is upside down relative to the carpenter, and secondly the currently available speed squares must be positioned on the far side of the common cut mark to be made, causing the carpenter to lean farther out from the roof. These two problems render the operation more difficult, more inaccurate and potentially more dangerous (in the case where the carpenter leans out too far and falls off the roof) than if the scale to be used for the rafter common cut mark were right side up relative to the carpenter and if the speed square could be used on the side closest to the carpenter of the mark to be made.